The present invention relates to a process for forming an inorganic material layer pattern on a substrate and, more specifically, to a pattern formation process suitable for the production of a plasma display panel, which enables the formation of a very fine pattern for a panel material forming each display cell of a plasma display panel and which can substantially improve workability using a transfer film compared with the process of the prior art.
Of flat panel display technologies, a plasma display panel (PDP) attracts much attention because its production process is easy though it is a large-sized panel and it has a wide view angle and is of a self light emission type with high display quality. Particularly, a color plasma display panel is expected to become the main stream of the market as a display device for 20-inch or more wall TVs in the future.
A color PDP can display colors by irradiating a fluorescent material with ultraviolet light generated by gas discharge. Generally speaking, the color PDP has a constitution such that fluorescent sites for emitting red color, fluorescent sites for emitting green color and fluorescent sites for emitting blue color are formed on a substrate so that light emitting display cells for respective colors are uniformly existent over the entire panel. Specifically, barriers ribs made from an insulating material are provided on the surface of a substrate made from glass or the like, many display cells are defined by the barrier ribs, and the inside of each display cell serves as a plasma function space. Each fluorescent site is formed in this plasma function space and an electrode for causing plasma to act on the fluorescent site is provided at this fluorescent site, whereby a plasma display panel comprising display cells as display units is formed.
FIG. 1 show an example of the structure of an AC type PDP. A pair of maintenance electrodes 6A are formed in the form of stripes on a front side substrate glass 1, a dielectric layer 3 covers the maintenance electrodes 6A and a MgO film 3A as a protective film is vapor-deposited on the dielectric layer 3. In FIG. 1, reference numeral 10 denotes bus lines.
To improve the contrast of the plasma display panel, red, green and blue colors filters and a black matrix (not shown) may be provided under the dielectric layer.
On a rear side substrate glass 2, signal electrodes 6B are formed in the form of stripes, barrier ribs 5 are provided between adjacent signal electrodes, and a fluorescent layer 4 is formed on the side and bottom of each of the barrier ribs 5.
The front side substrate and the rear side substrate are joined together and sealed in such a manner that the maintenance electrodes of the front side substrate and the signal electrodes of the rear side substrate cross each other at right angles, and a mixed gas of neon and xenon is introduced into the inside.
FIG. 2 shows an example of the structure of a DC type PDP. Cathode electrodes 6 a are formed in the form of stripes on the front side substrate glass 1.
On a rear side glass substrate, the electrode terminals and leads 6bxe2x80x2and 6cxe2x80x2of display anodes 6b and auxiliary anodes 6c are formed, and a resistor 7 is further provided between the anode terminal and the anode lead and between the auxiliary anode terminal and the auxiliary anode lead. The rear substrate is insulated with a dielectric 3 excluding the display anode terminals and the auxiliary anode terminals. Thereafter, to define a discharge space, barrier ribs 5 are provided in the form of a lattice and a fluorescent layer 4 is formed on the side and bottom excluding the anode terminal of each barrier rib. In FIG. 2, the reference numeral 8 denotes a display cell and the reference numeral 9 denotes an auxiliary cell.
The front side substrate and the rear side substrate are joined together and sealed in such a manner that the cathode 6a of the front side substrate and the display anode 6b and the auxiliary anode 6c of the rear side substrate cross each other at right angles, and a mixed gas of neon and xenon is introduced into the inside.
As a process for forming a pattern for panel materials such as the barrier ribs, electrodes, resistors, fluorescent materials, color filters and black matrix of the above plasma display panel, there are known (1) a screen-printing process which comprises screen-printing a non-photosensitive inorganic powder dispersed paste composition on a substrate to form a pattern and baking it; (2) a photolithography which comprises forming a photosensitive inorganic powder dispersed paste composition film on a substrate, exposing the film to ultraviolet light through a photomask, developing the exposed film to form a pattern on the substrate and baking it; and the like.
However, in the above screen printing process, the requirement for the positioning accuracy of a pattern is becoming more and more severe along with an increase in the size of a panel and a reduction in pattern width, and general printing cannot satisfy the requirement.
Also, in the above photolithography, the sensitivity in a depth direction of an inorganic powder dispersed paste layer is unsatisfactory and a very fine pattern with sharp edges cannot be always obtained when a 10 to 100 xcexcm-thick film pattern is to be formed with a one time of exposure and development.
It is an object of the present invention to provide a novel process for forming an inorganic material layer pattern on a substrate.
It is another object of the present invention to provide a process for forming a pattern suitable for the production of a plasma display panel.
It is still another object of the present invention to provide a process for forming a pattern having high dimensional accuracy.
It is a further object of the present invention to provide a process for forming a pattern, which can substantially improve workability and has excellent production efficiency as compared with the process of the prior art.
It is a still further object of the present invention to provide a transfer film having an inorganic powder dispersed paste layer for forming the above inorganic material layer, which is advantageously used to carry out the process of the present invention.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention can be attained by a process for forming an inorganic material layer pattern on a substrate (to be referred to as xe2x80x9cthe first process of the inventionxe2x80x9d), which comprises the steps:
(1) transferring an inorganic powder dispersed paste layer supported on a support film to the surface of the substrate to form the inorganic powder dispersed paste layer on the substrate;
(2) forming a resist film on the inorganic powder dispersed paste layer transferred to the surface of the substrate;
(3) exposing the resist film to light through a mask to form a latent image of a resist pattern;
(4) developing the exposed resist film to form the resist pattern;
(5) etching exposed portions of the inorganic powder dispersed paste layer to form an inorganic powder dispersed paste layer pattern corresponding to the resist pattern; and
(6) baking the pattern to form an inorganic material layer pattern.